Filament for incandescent electric lamps.



T. A. EDISON.-

FILAMENT FOR INCANDESCENT ELECTRIC LAMPS.

APPUCATION FILED MAY 31. 1901.

1,163,329. v. v Patented Dec. 7, 1915.

. ITED s'rAw THOMAS A. EDISON, or LLEWELLYN PARK, ORANGE, NEW JERSEY,AssIGNoE ro GENERALELEC'IRIC COMPANY, OF SCHENECTADY, NEW YORK, aCORPORATION OF NEW YORK.

FILAMENT FOR INCANDESGEN'I ELECTRIC LAMPS.

To all whom it may concern:

Be it known that I, THOMAS ALVA EDIsoN, a citizen of the United States,residing at Lewellyn Park, Orange, in the county of Essex and State ofNew Jersey, have invented certain new and useful Improvements in.Filaments for Incandescent Electric Lamps, of which the following is adescription.

My invention relates to improvements in filaments for incandescentelectric lamps, and process of making the same, and my object is toproduce a filament of an extremely refractory metal, such as tungsten ortantalum, of great homogeneity and of such extreme fineness that arelatively great resistance can be secured, whereby lamps of highvoltage and low candle-power can be made.-

The invention relates particularly to an incandescent electric lampfilament made of an extremely refractory metal, like tungsten ortantalum, resulting from the deposition of the metal electrically invacuo.

In Letters Patent of the'United States, No. 526,1d7, No. 713,863, andNo. 767,216, and dated respectively September 18th, 1894, November 18th,1902, and August 9th, 1904, I illustrate an improved process for platinga metal in oacuoupon a suitable receiving surface, whereby. films ofexcessive thinness can beobtained. I have usedthis process commerciallyfor forming a preliminary conducting coating on master phonograph crecords preparatory to electroplating the same in order to make moldsfrom which duplicate copies of said masters may be obtained, and in thephonographic art I have been enabled to thus plate a perfectly coherentand homogeneous film upon a master record of suchthinness as not toapprec ably affect the extremely shallow record groove, the maximumdepth of whichis somewhat less than one one-thousandth of an inch. By mypresent invention I am able to produce electric lamp filaments frommetallic tungsten and tantalum or other refractory metal, by a suitablemodification of the process disclosed in said patents, althoughvariations in said process may be adopted as will be apparent to thoseskilled in the art.

Specification of Letters Patent.

In order that the invention maybe better understood, attention isdirected to the accompanying drawings, forming part of thisspecification and in which I Figure 1, is a diagrammatic view of asuitable apparatus on which to deposit a film of the desired refractorymetal which is to be subsequently. formed into strips from which thefilaments may be made. Fig. 2,

a perspective view partly in section, illus- Patented Dec. "Z, 1915. I

Application fi led May 31, 1907. Serial No. 376,619.

trating the method of manufacturing tubular filaments of refractorymetal by my presout process, and Fig. 3, a corresponding viewillustrating the completed filament.

Referring to Fig. 1, I illustrate a base 1, carrying a suitable jar orglobe 2, so as to constitute a vacuum chamber from which the air isexhausted through a pipe 3. Mounted in the vacuum chamber is a support4, on which is rotatably mounted a suitable mandrel 5, carrying thecylindrical receiving' surface 6, which may be made of glass or of asuitable wax-like material. The mandrel 5 carries the bar magnet 7, andlocated outside of the globe is a magnet 8 rotated by suitable powerconnections engaging the pulley 9, so that by turning the magnet 8, themandrel 5 and the receiving surface within the conducting chamber willbe properly rotated. lhe glass arms 10 are located within the vacuumchamber and contain conductors 11 in circuit with the secondary 12 of asuitable induction coil. The primary circuit 13 of this coil is suppliedwith an alternating or pulsating cur rent from any suitable source.Suspended from the free ends of the arms 10 andin cir" cuit with theconductors 11 are electrodes 14-,

formed of the desired refractory metal. For example, in making theseelectrodes of tungsten they may be made, by subjecting pure metallictungsten in the form of powder toa sufficiently heavy compression as toefl'ect the" desired cohesion of the particles. For the manufacture ofelectrodes of other refractory metals, the same procedure may befollowed. By making use of metallic .electrodes as explained, within thevacuum chamber containing a rarefied or attenuated atmosphere, fromwhich oxygen has been excluded and by slowly rotating the receivingsurface :6 between them, the passage of the high tension alternatingcurrent between the electrodes Will result in the vaporization? of themetal which will be slowly deposited on the receiving surface togradually build up a film thereon of remarkable homogeneity of filamentsfor use in incandescent electric lamps. If desired the strips, afterbeing severed ;from the sheet, may be rolled over a suitable mandrel 15made of a soft metal or'wax and then bent into horseshoe shape, afterwhich the mandrel or core will be removed by melting or by dissolving itin a suitable solvent, leaving, as the final product, a tubular filament16, as shown in Fig.

3. The bending of the filaments may be readily effected by heating themetal to about 700 F. at which temperature metallic tungsten ismalleable. Or, if desired, a number of forms or mandrels 15 maythemselves constitute a receiving surface On which the metallic depositis made so as to result in the production of hollow seamless filaments,as will be understood.

4 By the process which I have described, perfectly homogeneous filamentscan be obtained of remarkably small cross sectional area, whereby themanufacture of lamps of high voltage and low candle power is permitted.Obviously, such a homogeneity I cannot be obtained where the metallicpowder is mixed with a suitable binder, -as is common.

Having now described my invention,what I clalm as new and desire'tosecure by Let-' ters Patent is as follows p Y 1. The process of forminga film for an incandescent lamp filament or filaments,

which consists in vaporizing tungsten by an I electric discharge, in'vacuo, and depositing the same on a surface in the path of thedischarge, substantially as set forth.

2.'The process of forming a..film for an incandescent lamp filament orfilaments,

whichconsists in vaporizing tungstenby an electric discharge in cacao,and depositing I the same on a revolving surface in the path of thedischarge, substantially as set forth.

3. 'The process of forminga film for an incandescent lamp filament orfilaments, which consists in vaporizing a difiicultly fusible metal byan electric discharge incacao, depositing the same on a surface in thepath of the discharge, and separating the film thus formed fromthesurface, substantially as set forth.

4. The process of forming a film for an incandescent lamp filament orfilaments,-

which consists in vaporizing a difiicultly fusible metal by an electricdischarge in cacao, depositing the same on a revolving surface in thepath of the discharge, and separating the film thus formed from thesurface, substantially as set forth. 5. The process of forming a filmfor an incandescent lamp filament or filaments, which consists invaporizing tungsten by an electric discharge in warm, depositing thesame on a surface in the path of the discharge, and separating the filmthus formed from the surface, substantially as set forth. 6. The processof forming a film for an incandescent lamp filament or filaments, whichconsists in vaporizing tungstenby an electric discharge in vacuo,depositing the same on a revolving surface in the path of the discharge,and separating the film thus formed from the surface, substantially asset forth.

7.. The process of forming a film for an incandescent lamp filament or Ifilaments,

which consists in forming electrodes by subjecting a difiicultly fusiblemetallic powder.

to compression s'uflicient to effect cohesion of the particles,vaporizing the -metallic powder by an electric glow discharge be- 1tween the electrodes, depositing the metal in a thin film on' areceiving surface in the path of the discharge, and separating the filmthus formed from the surface, substantially as set forth.

8. The process of forming afilm for an incandescent lamp filament orfilaments, which consists in forming electrodes by subjectingsubstantially pure metallic tungsten to" compression sufficient toeifectcohesion of the particles, vaporizing the tungsten by an electricglow discharge between the electrodes, and depositing the same in athi'nfilm on a receiving surfacein the path of the discharge, substantiallyas set forth.

9. The process of forming filaments for incandescent lamps, whichconsists in vaporizing adiificultly fusible metal by an .electricdischarge in vacuo, depositing the same in a thin homogeneous film on areceiving surface in'the path of the discharge, separating the film fromthe surface, cutting the-film into strips of suitable width,

rolling the strips over coresato form hollowtubes, and removingthecores,

substantially as set forth.

10.- The process of fo rming a filament for mcandbscent lamps, whichconsists in form hollow tube of minute cross-sectional area,

and bending the same into the form of a filament, substantially as setforth.

11. An electric lamp filament formed of a thin, homogeneous, coherentfilm of pure tungsten deposited from a vaporized c0ndi- 10 tion,substantially as described.

This specification signed and witnessed this 28th day of May 1907.

THOS. A. EDISON.

